Abstract

The cadmium (Cd) content in agricultural soils has increased during the last decades. This toxic heavy metal is allocated to edible plant parts and moves upwards in the food chain, e.g. via cereals and vegetables. Plant uptake has been investigated in many species. For wheat, most studies have focused on the concentration in the grain, not, as in this study, on total uptake.

The aim of this project was to determine the uptake of cadmium (Cd) in clone 78183 of willow (Salix viminalis L.) and two spring wheat (Triticum aestivum L.) cultivars, cv Dragon and cv Vinjett, as a function of both crop growth parameters, and Cd concentration in the growth medium. The correlation between Cd concentration in the soil and in the soil solution was also investigated. The concentrations in the growth medium were within the range of naturally occurring concentrations of Swedish agricultural land.

The experiment was carried out as a pot experiment under controlled conditions in a growth chamber. A blend of vermiculite, perlite, fine sand and fine gravel was used as growth medium, which was applied with cadmium sulphate to the concentrations of 0.00, 0.10, 0.25 and 0.40 µg g-1 dry soil respectively. Nutrients were supplied at an addition rate of 0.15 day-1 (i.e. the amount increased with 15% per day) to maintain the crop growth rate at steady state. Plant biomass above and below ground was measured by three harvests. The time of the experiment was six weeks. The concentration of Cd in the plants, soil and soil solution was analysed.

Cd uptake in plants was correlated to the Cd concentration in soil and in soil solution. Both species increased their uptake with increasing soil concentrations, but there was no significant difference in total uptake between the crops. Plant biomass production also affected the Cd uptake. When plants were grown in soil with the same concentration of Cd, the amount of Cd in the plant increased as the biomass increased. However, there was a difference between species. S. viminalis showed to be more efficient in taking up Cd per unit of biomass compared to the spring wheat cultivars. In S. viminalis, the amount of Cd in the leaves was higher than that in the roots and stems. On the contrary, roots of Dragon and Vinjett had higher amounts of Cd than the shoots.

The duration of growth, as well as concentration in the soil, influenced the uptake of Cd. Plants grown in low soil concentration for a long period may take up the same amount of Cd as plants grown in a high soil concentration during a shorter period. The conclusions were that the plant uptake increased as the concentration in the soil solution increased as well as the duration in time influenced the amount of Cd taken up. These results may be used for development of simulation models to predict plant uptake and to test the ability of plants to clean contaminated soils.